Method and device for personalizing luminescent marks of authenticity

ABSTRACT

A method and device for personalizing the luminescent authenticity features on data carrier, in particular plastic cards. The luminescent authenticity feature being applied to or incorporated in a composite card and the authenticity feature is personalized with a high-energy beam in that the intensity and/or wavelength of the beam is chosen such that local bleaching of the structure of the authenticity feature takes place.

BACKGROUND

1. Field of the Invention

This application relates to a method and apparatus for personalizingluminescent authenticity features.

2. Description of the Background

According to the prior art, it is possible to produce black markingsusing laser labeling systems. Use is made of this in laserpersonalization, which is used as an economic method with high qualityin many sectors and often also represents a security feature.

Furthermore, use is made of what are known as “UV colors” in securityfeatures. These “UV colors” are visible only to produce fluorescence orphosphorescence only when they are excited with UV light. They arepresent in printing inks or in fibers and are processed by variousprinting processes or added directly to the paper or plastic substrates.

One problem results from the fact that, in security technology, use ismade of what are known as “UV colors” which, because of fluorescence orphosphorescence, are visible only under UV light, but the securityfeatures developed from this cannot be personalized. Instead, in thecase of securities or plastic cards, for example, these features arepresent as printing or as an additive (fibers) in the paper or plastic.

SUMMARY

A method is therefore to be proposed with which laser markings onluminescent substances are possible, said markings being invisible undernormal conditions but visible with the aid of a UV light source oranother suitable excitation.

It is therefore an object of the invention to provide a method for lasermarking of new luminescent authenticity features or markings in whichthe marking produced is invisible in the normal state but becomesvisible with the aid of a UV lamp or via excitation in theelectromagnetic field, as a negative luminescent image (fluorescentimage or phosphorescent image).

The object is achieved by a method which provides for the activeluminescent pigments or dyes to be bleached with the aid of a laser oranother suitable energetic beam.

The invention therefore assumes a laser personalization of UV securityfeatures, for example in plastic cards, and combines the advantages oftwo methods, namely personalization by means of a laser beam and,moreover, the personalization of luminescent substances and theirverification under UV light or another high-energy excitation medium.

The invention claims in general the personalization of luminescentauthenticity features, no matter of what type, on any desired datacarriers. Also claimed as essential to the invention is in general thepersonalization of chemiluminescent and bioluminescent substances.Therefore, in the following description, the main term “luminescence” isused as a synonym for all three luminous phenomena.

In a preferred embodiment as claimed by the invention, the data carrierdescribed is a multilayer plastic card (for example in the form of acheck card). However, the invention is not restricted to this. Only forreasons of simplicity is the structure of a check card used below forthe further description of the invention.

Likewise, all possible incorporations and installation locations of theluminescent marking in a data carrier are claimed. The marking cantherefore be printed as printing ink onto a specific layer or aplurality of layers of the data carrier or applied in another way.However, the marking can also be incorporated into the plastic polymerof one or more of layers of the data carrier. The luminescent substancecan also be incorporated in the adhesive, the varnish or as an additivein the plastic material.

For further simplification, the term “UV color” is generally to beunderstood to mean a marking, substance or authenticity feature whichproduces luminous phenomena by utilizing photoluminescence and/orchemiluminescence and/or bioluminescence with the absorption ofhigh-energy light (normally ultraviolet light). Within the context ofthe invention, it is preferred that the luminous phenomenon appears invisible light. However, the invention is not restricted to this. For thedetection of the authenticity of check cards by machine, therefore, thisluminous phenomenon can also be provided in the invisible spectral rangeand evaluated by machine. Likewise, the invention is not restrictedeither to excitation with UV light; excitation in an appropriateelectromagnetic field can therefore also be provided, said field beingsuitable to cause the substance to luminesce (visibly or invisibly).

The various interactions between laser light and materials also includethe bleaching of chromophoric substances. In this case, according to theinvention, there is the possibility of destroying these chromophoricsubstances with the aid of a laser beam. For example, the body color ofa substrate containing pigments changes from colored to white.

This process is used in the context of the present invention.

One basic precondition for this process is that the chromophoricsubstance absorbs the laser light and enters into a chemical reaction inwhich it loses its colored characteristics. In the simplest case,chemical degradation of the chromophoric substance takes place. Inaddition, the laser light should not excite any side reactions whichlead to coloration of the substrate, and therefore do not effectbleaching to white.

The principle of bleaching with laser light may now, according to theinvention, also be transferred to “UV colors”, as they are known. These“UV colors” contain pigments or dyes which do not appear colored in thenormal case or are only weakly colored but, as a result of UV absorptionor other electromagnetic excitation, are excited to emit visible light.

The phenomenon is generally designated “cold illumination” orluminescence. Depending on the lifetime of the excited states, adistinction is drawn between fluorescence and phosphorescence, theemission taking place very quickly in the first case, but in the secondplace some post-luminescence also being observed following the UVexcitation.

The term “UV colors” is used frequently, but is used misleadingly, inthat most substances referred to in this way are not colored. Inaddition, the term “UV colors” is used in an inaccurate manner forUV-curing printing inks. In this case, the term UV does not refer toluminescent effects but the mechanism of the chemical curing duringprocessing.

In the bleaching of “UV colors” according to the invention, destructionof the chromophoric substance by means of intensive laser light iscarried out, analogous to the absorption colors. In this case, however,the substrate is not to be damaged in the visible range, nor is itscolored impression to be changed. It is therefore necessary for a (UV)wavelength range (band in the invisible range) to be selected, and theintensity must be metered in such a way that the UV color itself isexcited by the absorption and then breaks down, which corresponds tobleaching. In this way, bleaching with visible pigments would be made.

Since “UV colors” are not colored or only weakly colored under normalconditions, they absorb hardly any visible light. Therefore, ultravioletlight must be used for bleaching. In this case, a laser wavelength rangewhich is absorbed particularly well by the “UV color” used mustpreferably be selected.

“UV colors” which are suitable for bleaching by UV laser radiationbelong, for example, to the following

-   classes of substances:-   tin sulfide derivatives,-   benzoxazinone derivatives,-   pyrazoline derivatives.

For the purpose of bleaching the “UV colors”, in addition toultraviolet, infrared radiation and/or radiation of other wavelengthscan also be used if the chromophoric substances absorb the respectiveradiation used in the corresponding spectral range without visiblecoloration of the chromophoric substances occurring.

In a simple embodiment of the invention, the substrate to be markedexhibits uniform luminescence. This is achieved by means of a uniformapplication of “UV printing inks” or by incorporating the “UV colors” ina polymer matrix. The substrate can then be marked with the aid of thelaser by the “UV color” being locally bleached completely. In this way,for example, vector lines or halftone scanning images can be produced.Furthermore, there is the possibility of achieving partial bleaching bymeans of modulating the laser power and of generating gray-stage images.

In a further-reaching embodiment of the invention, even images printedwith “UV colors” or other security features which contain “UV colors”can also be marked subsequently.

The subject of the present invention is not just given by the subjectmatter of the individual patent claims but also by the combination ofthe individual patent claims with one another.

All the statements and features disclosed in the documents, includingthe abstract, in particular the physical embodiment illustrated in thedrawings, are claimed as essential to the invention if they are novel,individually or in combination, with respect to the prior art.

In the following text, the invention will be explained in more detailusing drawings which merely illustrate one possible implementation. Inthis case, further features essential to the invention and advantages ofthe invention emerge from the drawings and their description.

In the figures:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section through a card structure, illustrated insimplified form, the initial state of the method;

FIG. 2 shows a section through the card structure according to FIG. 1with the action of a laser beam;

FIG. 3 shows, schematically, a plan view of the structure according toFIG. 2;

FIG. 4 shows the card structure according to FIGS. 2 and 3 when excitedwith high-energy light;

FIG. 5 shows a plan view of the card structure according to FIG. 4.

DESCRIPTION

FIG. 1 shows a detail from a card structure in section, using sizerelationships that are not to scale. In this case, a luminescentauthenticity feature 3 is arranged on a carrier film 2. When illuminatedwith UV light 5, for example, the structure 4 is excited in such a waythat luminescence takes place, for example in visible light 6.

According to the invention, this authenticity feature 3 is now to bepersonalized. For this purpose, using a laser beam 7 (see FIGS. 2 and3), for example a line of text 8 is to be written into the structure 4of the authenticity feature 3. The intensity of the laser beam is chosensuch that the structure 4 is transferred into the structure 4′ only inthe region of the action of the laser beam. In this case, the structure4′ is not intended to have any structure or color change that can bedetected in visible light.

Only when irradiated with UV light 5 is the structure 4′ (see FIG. 5) nolonger to luminesce or to luminesce only weakly by luminescence; insteadthe intention is for only light 9 of a different color or even anegative image to appear in the overall luminescent image. The line oftext 8 written in therefore does not luminesce at all or lights up onlypartly or in a different color from that of the surrounding region.

If the luminescence is chosen by choosing the intensity of the laserbeam 7 such that only impairment of the luminescence but not extinctionoccurs, a halftone or gray-stage image to be detected as a line of text8 even when irradiated with a UV lamp 10.

Of course, the exemplary implementation explained here is not to beviewed as restrictive of the range of protection. All the variants andmodifications which have been described in the general part of thedescription apply. For example, irradiation with a UV lamp 10 is notrequired in order to make the authenticity feature 3 luminesce. Alsosufficient is excitation with radiation of different wavelengths in theinvisible spectral range and/or in an alternating electromagnetic field.

KEY TO DRAWINGS

-   1 Cover film-   2 Carrier film-   3 Authenticity feature-   4 Structure-   4′ Changed structure-   5 UV light-   6 Radiated light-   7 Laser beam-   8 Line of text (personalization)-   9 Radiated light-   10 UV lamp

1. A method of personalizing luminescent authenticity features on a datacarrier comprising: applying or incorporating a luminescent authenticityfeature in a composite card; personalizing the authenticity feature bybleaching with a high-energy beam; and modulating a parameter of thebeam such that local bleaching of the structure of the authenticityfeature takes place; wherein the bleaching completely destroys at leasta portion of a chromophoric substance of the luminescent authenticityfeature, and the destruction cannot be detected in visible light.
 2. Themethod as claimed in claim 1, further comprising modulating power of alaser beam in such a way that partial bleaching of the structure of theluminescent authenticity feature is achieved.
 3. The method as claimedin claim 1, further comprising luminescing the luminescent authenticityfeature under the action of an electromagnetic field.
 4. A device forimplementing the method as claimed in claim 1, wherein the high energybeam is a laser beam used for personalizing the luminescent authenticityfeature.
 5. The device as claimed in claim 4, wherein the luminescentauthenticity feature is caused to luminesce by photoluminescence.
 6. Thedevice as claimed in claim 4, wherein the luminescent authenticityfeature is caused to luminesce by chemiluminescence.
 7. The device asclaimed in claim 4, wherein the luminescent authenticity feature iscaused to luminesce by bioluminescence.
 8. The device as claimed inclaim 4, wherein luminescence of the luminescent authenticity featuretakes place in the visible spectral range.
 9. The device as claimed inclaim 4, wherein luminescence of the luminescent authenticity featuretakes place in the invisible spectral range.
 10. The device as claimedin claim 4, wherein the luminescent authenticity feature is excited byUV light.
 11. The device as claimed in claim 4, wherein the authenticityfeature is excited by IR radiation.
 12. A device for implementing themethod as claimed in claim 1, wherein the high energy beam is anelectron or neutron beam used for the personalization.
 13. The method asclaimed in claim 1, wherein the data carrier is a plastic card.
 14. Themethod as claimed in claim 1, wherein the parameter is the intensity ofthe high-energy beam.
 15. The method as claimed in claim 1, wherein theparameter is the wavelength of the high-energy beam.
 16. The method asclaimed in claim 1, wherein the bleaching of the luminescentauthenticity feature is configured to be irreversible.
 17. A method ofpersonalizing luminescent authenticity features on a data carriercomprising: applying or incorporating a luminescent authenticity featurein a composite card; personalizing the authenticity feature only bybleaching with a high-energy beam such that the bleaching completelydestroys at least a portion of a chromophoric substance of theluminescent authenticity feature, and the destruction cannot be detectedin visible light; and modulating a parameter of the beam such that localbleaching of the structure of the authenticity feature takes place.